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tracing: Support string type key properly 

The string in a trace event is usually recorded as dynamic array which
is variable length.  But current hist code only support fixed length
array so it cannot support most strings.

This patch fixes it by checking filter_type of the field and get
proper pointer with it.  With this, it can get a histogram of exec()
based on filenames like below:

  # cd /sys/kernel/tracing/events/sched/sched_process_exec
  # cat 'hist:key=filename' > trigger
  # ps
   PID TTY       TIME CMD
     1 ?     00:00:00 init
    29 ?     00:00:00 sh
    38 ?     00:00:00 ps
  # ls
  enable  filter  format  hist  id  trigger
  # cat hist
  # trigger info: hist:keys=filename:vals=hitcount:sort=hitcount:size=2048 [active]

  { filename: /usr/bin/ps                         } hitcount:          1
  { filename: /usr/bin/ls                         } hitcount:          1
  { filename: /usr/bin/cat                        } hitcount:          1

  Totals:
      Hits: 3
      Entries: 3
      Dropped: 0

Link: http://lkml.kernel.org/r/610180d6df0cfdf11ee205452f3b241dea657233.1457029949.git.tom.zanussi@linux.intel.com

Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
[ Added (unsigned long) typecast to fix compile warning ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Namhyung Kim 2016-03-03 12:54:53 -06:00 committed by Steven Rostedt
parent 69a0200c2e
commit 79e577cbce
1 changed files with 45 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

49
kernel/trace/trace_events_hist.c
View File

@ -52,12 +52,28 @@ static u64 hist_field_string(struct hist_field *hist_field, void *event)
return (u64)(unsigned long)addr;
}
static u64 hist_field_dynstring(struct hist_field *hist_field, void *event)
{
u32 str_item = *(u32 *)(event + hist_field->field->offset);
int str_loc = str_item & 0xffff;
char *addr = (char *)(event + str_loc);
return (u64)(unsigned long)addr;
}
static u64 hist_field_pstring(struct hist_field *hist_field, void *event)
{
char **addr = (char **)(event + hist_field->field->offset);
return (u64)(unsigned long)*addr;
}
#define DEFINE_HIST_FIELD_FN(type) \
static u64 hist_field_##type(struct hist_field *hist_field, void *event)\
{ \
type *addr = (type *)(event + hist_field->field->offset); \
\
return (u64)*addr; \
return (u64)(unsigned long)*addr; \
}
DEFINE_HIST_FIELD_FN(s64);
@ -340,7 +356,13 @@ static struct hist_field *create_hist_field(struct ftrace_event_field *field,
if (is_string_field(field)) {
flags |= HIST_FIELD_FL_STRING;
hist_field->fn = hist_field_string;
if (field->filter_type == FILTER_STATIC_STRING)
hist_field->fn = hist_field_string;
else if (field->filter_type == FILTER_DYN_STRING)
hist_field->fn = hist_field_dynstring;
else
hist_field->fn = hist_field_pstring;
} else {
hist_field->fn = select_value_fn(field->size,
field->is_signed);
@ -508,7 +530,10 @@ static int create_key_field(struct hist_trigger_data *hist_data,
goto out;
}
key_size = field->size;
if (is_string_field(field)) /* should be last key field */
key_size = HIST_KEY_SIZE_MAX - key_offset;
else
key_size = field->size;
}
hist_data->fields[key_idx] = create_hist_field(field, flags);
@ -841,8 +866,24 @@ static void event_hist_trigger(struct event_trigger_data *data, void *rec)
key = (void *)&field_contents;
if (hist_data->n_keys > 1) {
/* ensure NULL-termination */
size_t size = key_field->size - 1;
if (key_field->flags & HIST_FIELD_FL_STRING) {
struct ftrace_event_field *field;
field = key_field->field;
if (field->filter_type == FILTER_DYN_STRING)
size = *(u32 *)(rec + field->offset) >> 16;
else if (field->filter_type == FILTER_PTR_STRING)
size = strlen(key);
if (size > key_field->size - 1)
size = key_field->size - 1;
}
memcpy(compound_key + key_field->offset, key,
key_field->size);
size);
}
}
}